I saw it with my uncle recently, and I have to say that I was a bit disappointed. The stories were really lackluster and didn't catch my attention at all. The development from Bruce Wayne in Batman Begins to the Batman in Dark Knight could have been handled more fluidly, in my opinion.
However, the animation was great; and I guess that in itself makes it worth watching (at least as a rental). But it's definitely not a masterpiece :x